Optimization of Al Heavy Wire Bonds Bond profile in WBG Power Module Design

Abstract

Wide-Band Gap (WBG) semiconductors, such as SiC and GaN, have accelerated the ability to shrink the volumetric size and weight of power conversion systems by optimizing at the module level, due to their inherent high frequency, high temperature and high voltage capabilities. Power electronic module components, specifically flexible welded interconnects, behave like transmission lines at higher frequencies. Therefore, interconnects contribute to the power losses within the power module, and ultimately affect overall efficiency. Voltage and current overshoots and insertion/return losses and phenomena such as proximity and skin effect will also have a noticeable effect on the performance of the module as device switching is pushed into mid to high MHz range. Thus, to aid in design and development of advanced power modules this paper using FEA multiphysics solvers will firstly study the current carrying capacity and fusing time of different diameter Al heavy wire bonds interconnects. Then for a rated current, the multiple wire bond profile is considered to mitigate the negative effects from the fastest rising/fall edge of voltage and current switching high-frequency components. Characteristic impedance is then calculated using parasitic resistance and inductance for different wire bond profiles. The ultimate goal of the paper is to further the establishment of an evolution in thinking and designing when it comes to the WBG power electronic packaging practices and culture.